From: Sean Christopherson <seanjc@google.com>
To: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Zhao Liu <zhao1.liu@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Chao Gao <chao.gao@intel.com>, Xudong Hao <xudong.hao@intel.com>
Subject: Re: [PATCH 2/4] KVM: x86: Advertise AMX CPUIDs in subleaf 0x1E.0x1 to userspace
Date: Fri, 23 Jan 2026 09:53:26 -0800 [thread overview]
Message-ID: <aXO1lhrCb-y8oEnF@google.com> (raw)
In-Reply-To: <cf20fff4-931a-4a07-83c1-a33de13fa230@intel.com>
On Fri, Jan 23, 2026, Xiaoyao Li wrote:
> On 11/20/2025 1:07 PM, Zhao Liu wrote:
> > In addition to the new features, CPUID 0x1E.0x1.EAX[bits 0-3] are
> > mirrored positions of existing AMX feature bits distributed across the
> > 0x7 leaves. To avoid duplicate feature names, name these mirror bits
> > with a *_MIRROR suffix, and define them in reverse_cpuid.h as KVM-only
> > features as well.
>
> It looks that KVM can emulate the mirroring CPUIDs regardless of whether
> hardware supports subleaf 1. However, given such emulation provides no real
> benefit but complicates KVM implementation, this patch looks good to me.
Yeah, and it would run the risk of guest software doing stupid things like
assuming a certain CPU generation if the leaf is supported.
next prev parent reply other threads:[~2026-01-23 17:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-20 5:07 [PATCH 0/4] KVM: x86: Advertise new instruction CPUIDs for Intel Diamond Rapids Zhao Liu
2025-11-20 5:07 ` [PATCH 1/4] KVM: x86: Advertise MOVRS CPUID to userspace Zhao Liu
2026-01-23 18:03 ` Sean Christopherson
2025-11-20 5:07 ` [PATCH 2/4] KVM: x86: Advertise AMX CPUIDs in subleaf 0x1E.0x1 " Zhao Liu
2026-01-23 6:02 ` Xiaoyao Li
2026-01-23 17:53 ` Sean Christopherson [this message]
2026-01-23 17:55 ` Sean Christopherson
2026-01-25 7:51 ` Zhao Liu
2026-01-23 18:06 ` Sean Christopherson
2026-01-25 7:54 ` Zhao Liu
2025-11-20 5:07 ` [PATCH 3/4] KVM: x86: Advertise AVX10.2 CPUID " Zhao Liu
2025-11-20 5:07 ` [PATCH 4/4] KVM: x86: Advertise AVX10_VNNI_INT " Zhao Liu
2025-12-18 17:54 ` [PATCH 0/4] KVM: x86: Advertise new instruction CPUIDs for Intel Diamond Rapids Paolo Bonzini
2026-01-21 1:40 ` Zhao Liu
2026-01-23 6:03 ` Xiaoyao Li
2026-02-04 0:10 ` Sean Christopherson
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